cf822D(质因子)

 1 #include <iostream>
 2 #define ll long long
 3 using namespace std;
 4 
 5 const int mode = 1e9 + 7;
 6 const int MAXN = 5e6 + 10;
 7 int prime[MAXN];
 8 
 9 void get_prime(void){
10     for(int i = 2; i < MAXN; i++){
11         if(!prime[i]){
12             for(int j = 1; j * i < MAXN; j++){
13                 if(!prime[i * j]) prime[i * j] = i;
14             }
15         }
16     }
17 }
18 
19 ll get_f(ll n){
20     ll ans = 0;
21     while(n > 1){
22         ll cnt = prime[n];
23         ans += cnt * (cnt - 1) / 2 * (n / cnt);
24         if(ans >= mode) ans %= mode;
25         n /= cnt;
26     }
27     return ans;
28 }
29 
30 int main(void){
31     get_prime();
32     ll t, l, r, ans  = 0, cnt = 1;
33     cin >> t >> l >> r;
34     for(ll i = l; i <= r; i++){
35         ans += cnt * get_f(i);
36         if(ans >= mode) ans %= mode;
37         cnt = cnt * t % mode;
38     }
39     cout << ans << endl;
40     return 0;
41 }